Acoustic transponder



c; H. ODONNELL ETAL 3,316,529

April 25, 1967 ACOUSTIC TRANSPONDER 3 Sheets-Sheet 2 Filed Aug. 26, 1964 IN V EN T ORS CHARLES H. ODOlV/VE LL JOHN S. TAME April 7 c. H. ODONNELL ETAL 3,316,529

ACOUSTIC TRANSPONDER Filed Aug. 26, 1964 3 Sheets-Sheet 5 Q (D) M FREQ \I Q (E) I as 4WW-1W/L 82 FIG 6 FIG 8 i as (B) -\fL/W1/ M Q: E 84 UWMT g o FREQ w) VWU\J M M F/G 7 (E) v F G 9 INVENTORS CHARLES H. ODONA/ELL JOHN 5. TA ME A r Tomi/E rs United States Patent Ofilice 3,316,529 ACOUSTIC TRANSPONDER Charles H. UDonnell, Willowick, and John S. Tame,

Cleveland Heights, Ohio, assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Aug. 26, 1964, Ser. No. 392,344 1 Claim. (Cl. 340-2) The present invention relates generally to transponders and in particular is an acoustic transponder that is adapted for being submerged in sea water in order to broadcast a. predetermined acoustical energy therein in response to a predetermined received signal for navigation or other reference purposes.

In the past, it has been difficult to make a completely self-contained transponder which may be easily positioned at a preferred submarine position without the necessity of employing mounting apparatus, special launching apparatus, external activating apparatus, and sea divers or the equivalent for actually installing and otherwise placing it in useful position. One of the reasons for the existence of the above disadvantages is the fact that most of the prior art devices of this type are sufficiently complex, both mechanically and electrically, as to require special handling, thereby creating an undue burden from an operating personnel standpoint, as well as from a manufacturing standpoint.

The present invention substantially eliminates most of the disadvantages of the prior art devices in that the subject transponder is relatively simple, both electrically and electronically, and, moreover, incorporates a simple but important and expeditious method and means of operationally activating it at a predetermined water depth, while allowing it to retain a compact unitary structural configuration for storage and launching purposes.

It is, therefore, an object of this invention to provide an improved transponder.

Another object of this invention is to provide an improvide acoustical transponder that may be stored and launched as a unitary device and subsequently exploded to an operable and useful condition at a predetermined depth after being disposed within sea water or other appropriate environmental medium.

Another object of this invention is to provide a transponder that may be launched by free-fall from a marine, submarine, air, or space craft.

Still another object of this invention is to provide an improved transponder which receives a predetermined transmitted pulse and initiates a return pulse in response thereto in order to, in turn, provide range and bearing information.

A further object of this invention is to provide an improved navigation aid.

Another object of this invention is to provide a transponder that is easily and economically manufactured, maintained, and automatically operated.

Other objects and many of the attendant advantages of the subject invention will be recognized and appreciated as it becomes better understoodby reference to the following detailed description, when considered in conjunction with the accompanying drawing, wherein like reference characters designate corresponding elements in the several views, and wherein:

3,316,529 Patented Apr. 25, 1967 V therein;

FIG. 2 is a block diagram of the transducer and the receiver and transmitter electronic circuitry incorporated in the transponder of FIG. 1;

FIG. 3 is a detailed schematic diagram of the respective components shown in block form in FIG. 2;

FIG. 4 is a detailed schematic diagram of the squib and exploding circuitry therefor incorporated in the representative transponder of FIG. 1;

FIG. 5 is a pictorial view of one representative use of the instant invention;

FIG. 6 depicts exemplary waveforms of output signals from various and sundry components incorporated in they receiver and transmitter portions of the invention during normal receive and transmit conditions;

FIGS. 7 and 8 represent frequency response curves occurring as a result of the unique construction of the narrow band discriminator portion of this invention; and

FIG. 9 illustrates exemplary waveforms which occur in the transmitter and receiver sections of the invention when the subject transponder hears or receives its own transmission.

Referring now to FIG. 1, the transponder constituting this invention is shown as having a casing 11 containing a float 12, an electroacoustical transducer 13 coupled by a reeled line 14 between said float and an electronic circuitry section 15, likewise included within casing 11. A squib 16 and exploding circuitry 17 therefor and a hydrostatic pressure switch 18 also housed in casing 11, along with a power supply 19, which supplies the electrical energy required by each of the aforementioned electrical components, respectively. In this representative embodiment, power supply 19 takes the form of a battery but it should be understood that any other suitable power supply may be employed as desired.

At some desired location 21 along the longitudinal axis of transponder casing 11, said casing is designed to be separated by squib 16 so as to enable the release of float 12 and transducer 13 to an operable submarine position, as will be explained in more detail below in connection with the discussion of the operation of the invention.

Referring now to FIGS. 2 and 3, transducer 13 is depicted as having the output thereof coupled to a receiver 22 through a transmit-receive (TR) type amplitude limiter 23. The output of limiter 23 is then coupled to the input of a first RF amplifier 23, the output of which is coupled to the input of a second RF amplifier 25, the output of which is connected to the input of another amplitude limiter 26 of the type that limits the value of positive or negative voltage to be passed thereby to an acceptable value or operational voltage. The output of limiter 26 is fed to a third RF amplifier 27,with the output thereof coupled to the input of a tuned bandpass filter 28 and detector 29 combination which in effect comprises an extremely narrow band frequency discriminator 31. The output thereof is coupled to a direct current amplifier 32, the output of which constitutes the output of the aforesaid receiver portion 22.

The output of receiver 22 is then supplied to the input of a transmitter portion 33 and particularly, in this case,

it is supplied to a one shot timer 34. This one shot timer may, if desired, be of the monostable multivibrator type which produces a substantially square wave output for every input signal of positive polarity supplied thereto. An oscillator 35 is coupled to the output thereof for producing a pulsed C.W. signal having a frequency that is proportional to the amplitude of the aforementioned square wave and a duration or ping length proportional to the length of the positive portion of said square wave.

The output of oscillator 35 is then amplified in a driver amplifier 36 and a power amplifier 37 before being coupled to transducer 13 for broadcast thereby. The foregoing, of course, generally makes up electronic circuitry 15 which is suitably disposed in transponder casing 11, as mentioned above.

FIG. 3, of course, is depicted as to illustrating schematic details of the herein disclosed preferred embodiment, and, although for the most part, the particular stages or elements involved that have been shown in block form are conventional per se, several items would appear to be of sufiicient uniqueness in this particular arrangement to warrant further discussion thereof. Specifically, the items referred to are limiter 23, limiter 26, and the so-called narrow-band frequency discriminator 31.

Limiter 23 is actually a device which effectively acts as a special type TR tube in that it very accurately limits the positive and negative current swings to predetermined values, thereby allowing only the passage of voltages having predetermined amplitudes or less. A pair of reversed diodes 51 and 52, preferably of the IN2069 type, easily and economically effect this result.

Limiter 26 contains a pair of diodes 53 and 54, preferably of the IN461 type, which are likewise reversed so as to function in a manner similar to diodes 51 and 52 of limiter 23, and thereby delete unwanted or spurious amplitude signals from any signal passing therethrough at any given instant.

Discriminator 31 also appears to be unique in its construction and results and is particularly well suited for incorporation in this invention because it selects, refines, shapes, and passes with extreme accuracy only a very narrow band of frequencies. This, in turn, enables the subject transponder to respond only when interrogated by the predetermined transmitted sonar signal of a friendly vessel during naval operations or a navigating vessel having knowledge of the proper frequency signal to send thereto. Discriminator 31 is shown as having a transformer 55 having a primary winding 56 and a secondary winding 57 with a capacitor 58 coupled across the primary winding thereof and a positive sixteen volts connected to one terminal thereof. Secondary winding 57 has a diode 59, preferably of the IN461 type, connected in series therewith and a resistor 61 and a capacitor 62 each connected in parallel with said series connected secondary winding and diode. A sixteen volt positive voltage is also coupled to one terminal of secondary winding 57. Another transformer 63 has a primary winding 64 and a secondary winding 65 with a capacitor 66 connected in parallel with primary winding 64. Secondary winding 65 has a diode 67 connected in series therewith and a resistor 63 and a capacitor 69 connected in parallel with said series connected secondary winding 65 and diode 67. One terminal of primary winding 64 is electrically coupled to an intermediate turn of primary winding 56 of transformer 55, and one terminal of secondary winding 65 is connected to the output of diode 59. Still another transformer 71 has a primary winding 72 and a secondary winding 73 with a capacitor 74 connected in parallel with primary winding 72. A diode 75, preferably of the IN461 type, is series connected with secondary winding 73, and a resistor 76 and a capacitor 77 is connected in parallel with said series connected secondary winding 73 and diode 75. One terminal of primary 72 is electrically connected to a predetermined turn of primary winding 64 of transformer 62. and one terminal of secondary winding 73 is connected to the output of diode 67. The input to discriminator 31 is connected to a predetermined turn of primary winding 72 of transformer 71 and the output thereof is taken from the output of diode 75. If each of the aforesaid transformers and their respectively associated components are considered to be individual sections 81, 82, and 83, respectively, it may be seen that only three of such sections are included in discriminator 31, but it should be understood that any desired number thereof may be included therein to provide any desired frequency response curve. So doing would obviously be well within the purview of one skilled in the art having the benefit of the teachings herein presented.

FIG. 4 discloses in more detail the squib firing circuitry, as well as the power supply and pressure switch. Squib 16 may be of any desired conventional explosive type which, for example, may contain an ignitor charge, a slow-burning time delay charge, and a bolt-exploding charge of sufficient strength to properly separate the transponder casing sections to release float 12, transducer 13, and line and/ or cable 14 connected thereto and to the aforesaid receiver 22 and transmitter 33.

Squib 16 contains a firingmeans, such as an ignitor wire 41, which is connected to battery 19 and ground through any conventional and suitable connector bus 42 and fuse 43 in such manner as to be fired whenever hy= drostatic pressure switch 18 is closed. Capacitors 44 through 47, which may be of the order of 25 volt-543 microfarad capacitors each, are effectively connected in parallel with ignitor 41. A resistor 48 is likewise c'ori-' nected in parallel with said ig'nitor 41 and capacitors 44 through 47. The positive terminal of battery 19 supplies the positive voltage, say of the order of +16 volts, to all of the aforesaid electrical and electronic equipments, such as receiver 22 and transmitter 33, for the powering there= of, as well as to squib 16 for the timely firingthereof.

The operation of the transponder constituting this im vention will now be discussed briefly in connection with FIGS. 5 through 9 as well as the aforementioned FIGS; 1 through 4.

A ship 51 or other craft which may desire to navigate safely along a predetermined path within a known chan= nel or through other known obstacles may do so with rela-' tive ease, confidence, and safety if said path contains transponders of the type herein describedthat are periodi cally spaced to act as reference points from which said ship may determine its position at any given instant by merely taking range and bearing measurements thereon. Such measurements are effected by acoustically pinging on the transponders and then listening for their respective return signals.

But before such operations may occur, it is first neces sary to locate the transponders in the proper guiding posi-' tions and actuate them to an operative condition. This is done by dropping each transponder into the water at its desired and proper location. As it descends to a predetermined depth, say of the order of eleven feet, the water pressure causes hydrostatic pressure switch 18 to close, thereby sending sufficient current to explode squib 16 and simultaneously separate transponder casing 11 at predetermined joint or connection means 21. For this purpose, any conventional connection and separation structure that is convenient and appropriate may be used, such as, for example, explosive bolts or the like. As soon as squib 16 is fired, the conductor thereto becomes shorted by the water and this, in turn, overloads fuse 43 and blows it. Hence, the fuse circuit thereafter remains open and in an otherwise safe condition without adversely affecting the power supply portion thereof. However, before the intentional ignition of squib 16, it remains in a relatively safe condition due to the presence of resistor 16 which acts as a load resistor to absorb any small stray cur-rents that may be inadvertently applied to said squib from any source, either power or other (such as static electricity,

electromagnetic energy, or the electrical equivalent thereof).

The separation of transponder casing 11 also effects the release of float 12, transducer 13, and electrical cable 14 connected thereto and to the transmitter 33 and receiver circuits. After such release, said elements take substantially the position illustrated in FIG. 5 and, of course, each are properly energized and interconnected so as to cooperate to effect transmission of acoustical energy throughout the ambient submarine environment in response to receipt of acoustical energy broadcast by interrogating ship 51. In actual operation, the response frequency of receiver 22 and the transmit frequency of. transmitter 33 are preferably different and so designed to provide optimum navigational results or maximum security of communication, as desired, with minimum interference therebetween. This, being a matter of design choice, would be obvious to the artisan having the benefit of the teachings herein presented.

For specific information regarding the receive-transmit operation, attention is directed to FIGS. 2, 3 and 6 through 9. When interrogated by ship 51, transducer 13 received the acoustical energy therefrom and converts it into equivalent or proportional electrical energy of the type exemplarily represented in FIG. 6 (A). Because this electrical energy is not of sufficient amplitude or voltage in either the positive or negative direction, it passes through TR limiter 23 without triggering either of diodes 51 or 52 into a conductive state. This electrical energy is then amplified by RF amplifiers 24 and 25, passed through another TR type limiter 26 because it still is not of sufficient amplitude to effect conduction of diodes 53 or 54, and reamplified by RF amplifier 27 before being applied to narrow band discriminator 31 (see FIG. 6 (B) As previously mentioned, narrow band discriminator is a somewhat unique circuit and produces an output signal only if the input signal thereto falls within an extremely narrow band of frequencies. This result is effected due to the circuit arrangement of discriminator 31 shown in detail in FIG. 3 which, in turn, has a final frequency response curve similar to that exemplified by FIG. 7. Because diodes 59 and 75 have polarities which are reversed relative to that of diode 67, three frequency response curves are formed with the two former ones oppositely directed from the latter, as shown in FIG. 8. However, as a result of the other element interconnections and properly reversed windings of the respective transformers all curves are made algebraically additive (as shown in FIG. 7), leaving only the cross-hatched area covering the frequencies that Will be passed. In other words, those bandpass frequencies of curves 82 and 83 are subtracted from the band-pass frequencies of curve 81 to leave the very narrow pass band frequencies 84 falling Within the aforementioned cross-hatched area.

Incorporation of narrow band discriminator 31 in this invention facilities increasing the accuracy of response to predetermined interrogation signals by making it considerably more responsive thereto while rejecting all other unwanted interrogation signals or other signals such as unfriendly interrogation signals, signals produced by natural causes, and other spurious signals.

When the proper frequency input signals are applied thereto, discriminator 31 produces an output signal of the type exemplarily represented by the wave form of FIG. 6 (C). This waveform, in turn, becomes the type represented in FIG. 6 (D) after amplification and rectification by D.C.'amplifier 32, which, incidentally, also acts as an isolation cathode follower type (collector follower type in this particular embodiment, since a 2Nl23l type transistor is preferably used therein) of the circuit.

Each initial positive voltage rise from DC amplifier 32 kicks one shot timer 34 to produce the square wave output signal depicted in FIG. 6 (E), and this, in turn, effects actuation of oscillator 35 to cause the type of signal similar to that illustrated in FIG. 6 (F) to be produced. The frequency of this oscillator output signal is proportional to the amplitude of the square wave output signal from one shot timer 34 and it has a pulse or ping duration equal to the length of time or period of the positive portion of said square wave. After being appropriately amplified by driver amplifier 36 and power amplifier 37, this signal is supplied to transducer 13 for broadcast thereby.

Because the subject transponder hears or receives itself When it is transmitting, said transmitted signal must be stopped somewhere in the system to prevent regenerative system oscillation from occurring. This is accomplished by limiters 23 and 26 which respectively conduct at a predetermined voltage that is considerably lower than the voltage of the signal transmitted by the transponder. Hence, these limiters effectively act as transmitreceive (TR) devices to stop, for all practical purposes, most of the heard transmitted signal.

FIG. 9 (A) again represents the transmitted signal from the subject transponder but on a different time basis than shown in FIG. 6 (F). It is, thus, clipped to become the waveform of FIG. 9 (B) after passing limiter 23, amplified to become the waveform of FIG. 9 (C) by amplifiers 24 and 25, and again clipped to become the waveform of FIG. 9 (D) after being processed by limiter 26. This signal is then effectively applied to discriminator 31 Where it becomes the waveform exemplarily illustrated in FIG. 9 (E). Because it is of small amplitude and because it does not fall within the very narrow pass band frequency, the output of discriminator 31 is a relatively low amplitude negative signal rather than a positive signal, and since D.C. amplifier 32 will not pass a negative signal, no signal (represented by FIG. 9 (F)) is produced thereby. This, in turn, prevents one shot timer 34 from being inadvertently actuated, inasmuch as it requires a positive input signal to do so. Of course, if one shot timer 34 is not actuated by a positive input thereto, it will not produce its square-wave output, oscillator 35 will not be actuated, and no signal will be supplied to transducer 13. Thus regenerative system oscillation is prevented.

Although the preferred embodiment of the transponder constituting this invention has been disclosed as being operated in an underwater environment, it should be understood that it may be so designed by the skilled artisan as to operate in any other desired environment where it may be used to an advantage Without violating the legal scope and spirit of the invention. So doing would obviously be within the purview of said artisan having the benefit of the teachings herein presented.

Therefore, many modifications and other embodiments of the subject invention will readily come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing description and accompanying drawing of the subject transponder, and hence, it is to be understood that the invention is not to be limited thereto and that said modifications, etc., are intended to be included within the scope of the appended claim.

What is claimed is:

An acoustic transponder comprising in combination:

a reversible transducer for broadcasting an acoustical output signal in response to an electrical input signal and for producing an electrical output signal in response to an acoustical input signal;

a first limiter connected to the electrical output of said transducer;

first radio frequency amplifier means connected to the output of said first limiter;

a second limiter connected to the output of said first radio frequency amplifier means;

a second radio frequency amplifier means connected to the output of said second limiter;

a tuned band-pass filter connected to the output of said second radio frequency amplifier means;

timer; and

amplifier means connected between the output of said oscillator and the electrical input of the aforesaid 10 transducer.

References Cited by the Applicant UNITED STATES PATENTS 6/1949 Hayes et al. 1s1 .s 1v 9/1952 Wilmotte 325-344 8 3/1960 Ruehlemann 10270.2 6/ 1963 Tatnall et a1 340-2 9/1963 Naeseth 10222 10/ 1965 Hagemann 340--3 FOREIGN PATENTS 9/ 1960 Great Britain.

OTHER REFERENCES Wasik, J. W., Undersea Transmitters To Locate Missile Impacts. In Electronics. 36 (7); p. 18, Feb. 15, 1963.

BENJAMIN A. BORCHELT, Primary Examiner.

W. KUJAWA, Assistant Examiner. 

